Interaction Region Vacuum Chamber Upgrades Presented by: Scott DeBarger Contributors: D. Arnett, B. Bigornia, C. Carr, J. Langton, S. Metcalfe, D. Kharahk, M. Kosovsky, N. Kurita, R. Pope, N. Reeck, A. Sheng, B. Smith

Interaction Region Vacuum Chamber Upgrades p.2 of 25 Outline m Forward Q2 Chamber m Q1/Q2 HOM Bellows m HER Q4 & Q5 Vacuum Chambers; HOM Absorbing Bellows m LER Q4 R Temporary Chamber m LER Q4 & Q5 Vacuum Chambers m DS-7 Transition m LER 2062 Chamber m LER 2143 Collimator m Interaction Region HOM Absorbers m Additional Diagnostics m HOM Straight Bellows

Interaction Region Vacuum Chamber Upgrades p.3 of 25 m Replaced Q2R with a Q2L chamber in 2002  Improve Beam Stay-Clear and reduce HOM generation (see mask at right)  Chamber failed (following operation) due to material flaw in the GlidCop m Original Q2R chamber reinstalled in 2003  Does not maintain Beam Stay-Clear  No evidence that it creates increased HOMs m New Q2R installed March 2006  Opportunistic installation in conjunction with Q1/Q2 bellows seal  Still no effect on HOM generation observed Forward Q2 Chamber

Interaction Region Vacuum Chamber Upgrades p.4 of 25 m Identified as a critical upgrade at previous review m Technically very challenging  Limited space available  Anticipated high power loads m Design compromises travel during installation to accommodate new HOM absorption arrangement m 61 mm maximum tile/slot length m Absorbing tiles are open to the convolutions  No additional tile set needed in bellows cavity m HER Arc Bellows features  Spring, Stub, RF shield m (See M. Sullivan talk) Q1/Q2 HOM Bellows

Interaction Region Vacuum Chamber Upgrades p.5 of 25 Q1/Q2 HOM Bellows m RF Seals replaced 22 February 2006 (see M. Sullivan talk) Installed design New stub in fabrication Materials in hand (AlN-SiC tiles, GlidCop, bellows) Working aggressively to complete new bellows modules Hope to install during current shutdown

Interaction Region Vacuum Chamber Upgrades p.6 of 25 HER Q4 & Q5 Chambers m HER Q5 & Q4 Chambers  General issues  Mechanical & HOM failures in the NEG screens  Beam Stay-Clear (BSC) & Luminosity cone restrictions  Thermal motion of magnets l Original Q4 & Q5 are rigid chambers that have minimal to no clearance to their respective magnets  Global alignment errors between the 10-meter Collimator and Q5 L and between Q5 R and High Power Dump.  History of mask and flange failures due to SR heating  NEG heating during high current operation

Interaction Region Vacuum Chamber Upgrades p.7 of 25 m Design goals (achieved)  LER: 4.5A, HER 2.2 A operation  Respect the defined BSC/Luminosity cone and existing magnet envelopes.  Maintained a 2mm gap to poles and a 3mm gap to coils  Reduce operating thermal gradients  Improve kinematics and stabilize BPMs  Added a bellows between Q4, Q5  Added a flex flange between Q2L & Q4L  Replaced beampipe supports  Decrease the RF leakage to the pumps  Screen hole diameter reduced to 3 mm and depth increased to 6mm HER Q4 & Q5 Chambers Q5 NEG RF Screen

Interaction Region Vacuum Chamber Upgrades p.8 of 25 HER Q4 & Q5 Chambers m HER Q5 L Chamber  Installed Fall 2005 m HER Q4 & Q5 R and HER Q4 L Chambers  Installed beginning in August 2006  Installation revealed vertical misalignment of ~9 mm at HER High Power Dump (corrected) Q5 L installation m Aluminum clamshell design  Profile matched to available space  Excellent assembly distortion control  Straightness in y-z (vertical) plane = +/-.030”  Straightness in x-z (horizontal) plane = +/-.011”  End to end roll = 9 mRad

Interaction Region Vacuum Chamber Upgrades p.9 of 25 Performance of Q5 L Chamber m HER Q5 L  Installed Fall 2005  Beam induced heating of NEG dramatically reduced HER Current (Mar 05-Aug 06) Temperature of Q5 L NEG (Mar 05-Aug 06)

Interaction Region Vacuum Chamber Upgrades p.10 of 25 Q4 side, 10” flange Q5 side 12” flange GlidCop Stub Inconel Spring Finger GlidCop RF Shield Finger Welded Bellows Cooling – not shown Absorbing Tile m Mechanically decouples Q4 & Q5 vacuum chambers m Absorbing tiles above and below beam orbit Q4/Q5 Bellows with Absorber

Interaction Region Vacuum Chamber Upgrades p.11 of 25 LER Q4 Right Temporary Chamber m LER Q4 R chamber replaced by a straight drift tube on 22 February 2006 m Concern that the chamber outgassing and/or sparking caused beam aborts (found to be not true).

Interaction Region Vacuum Chamber Upgrades p.12 of 25 LER Q4 & Q5 Chambers m Two major issues addressed in redesign  Beam induced NEG heating (leading to NEG outgassing)  Thermal motion of the Q2,4,5 raft/magnets m New design for LER Q4 & Q5  Improved RF screens  Added “Flex Flange” at chamber inboard ends  Improved mask cooling; also additional cooling added Old ScreenNew Screen “Flex Flange” detail

Interaction Region Vacuum Chamber Upgrades p.13 of 25 LER Q4 & Q5 Chambers m Status  Chamber fabrication and assembly complete  Q4 vacuum processing complete; Q5 chambers are on bake  Ready to begin installation of Q4 when project engineer returns on 26 October “Flex Flange” prior to final assembly

Interaction Region Vacuum Chamber Upgrades p.14 of 25 LER Q4 & Q5 Chambers m Status  Chamber fabrication and assembly complete.  Q4 vacuum processing complete; Q5 chambers are on bake.  Ready to begin installation of Q4 when project engineer returns on 26 October

Interaction Region Vacuum Chamber Upgrades p.15 of 25 DS-7 Octagonal-to-Round Transition m Chamber absorbs a large amount of LER SR originating near the IP ( A, 3.1 GeV) m Previous DS-7 chamber not well cooled m New chamber incorporates GlidCop body and improved cooling m Installed Nov 2005

Interaction Region Vacuum Chamber Upgrades p.16 of 25 LER 2062 Chamber m Vacuum leak developed on 10 Dec sealed temporarily. m LER 2062 chamber replaced 1 May 2006 m Buttons in nearby chambers fell on 2 & 5 May, prompting effort to remove LER Collimator m Repaired chamber reinstalled on 16 May chamber

Interaction Region Vacuum Chamber Upgrades p.17 of 25 LER 2143 Collimator m LER 2143 Collimator removed 16 May 2006  Intended to control backgrounds in BaBar  HOM generator affecting downstream LER  Damage to the collimating surface being evaluated

Interaction Region Vacuum Chamber Upgrades p.18 of 25 Interaction Region HOM Absorbers m High current running prompts a desire to manage HOM heating in the LER m Two HOM absorbing chambers to be added to the LER (3044 & 1153) m RF Shield 3.5 mm slots in 2.5 mm thick GlidCop Uses Ceralloy 13740Y (Aln-SiC) tiles Matches existing LER Octagonal cross section Install November 2006 Absorption (calculated by S. Novokhatski, S. Weathersby): Monopole – % Dipole – 54% Other Dipole – 88% Quadrupole – 89% Design selected for high absorption over a broad frequency range All absorption curves relatively flat – no major spikes or troughs

Interaction Region Vacuum Chamber Upgrades p.19 of 25 Interaction Region HOM Absorber (1153) HOM Absorber Octagonal to LER Arc Transition (New) Elliptical to Octagon Transition Octagonal Bellows e+e+ Octagonal to Elliptical Mask (New) Elliptical VAT Valve (reinstalled) Improved masking at 1153 location

Interaction Region Vacuum Chamber Upgrades p.20 of 25 Additional Diagnostics m Vacuum gauges added  9 additional hot filament gauges distributed through the Interaction Region  These gauges are less sensitive to non-vacuum beam effects

Interaction Region Vacuum Chamber Upgrades p.21 of 25 Additional Diagnostics m Fast(er) data sampling  SLAC standard history buffers store at 6 minute intervals  Data Archiver stores specified channels at 1 second intervals

Interaction Region Vacuum Chamber Upgrades p.22 of 25 Additional Diagnostics m (Really Fast) Abort Logger  Multiple channels for  10 seconds surrounding a beam abort  To date, only in place in IR-2; all other IRs added this downtime m Digital Video Recorder, Rotating Mirror, …

Interaction Region Vacuum Chamber Upgrades p.23 of 25 m Goal – to create a HOM absorber in a defined modular space  HOM absorber will damp and absorb the power, preventing neighboring components from absorbing excessive HOM power m Design optimized with MAFIA simulations m Installed one unit on 1 May 2006 m Three additional units deployed in Oct 2006 HOM Straight Bellows

Interaction Region Vacuum Chamber Upgrades p.24 of 25 Modes that leak past the RF shield finger still see the absorber HOM Straight Bellows m Measurements confirm that the straight bellows-absorber in Region damped 40% of the available HOM power m Very good agreement with calculated performance of a 7cm length absorber

Interaction Region Vacuum Chamber Upgrades p.25 of 25 Summary m The Interaction Region Vacuum System is receiving a major reworking in 2006  Principal efforts are centered around high current running  Management of synchrotron radiation and higher order mode heating has been addressed  Diagnostic capabilities have been developed and implemented to improve our abilities to understand future problems should they arise m We feel that the Interaction Region vacuum system will be ready to meet the demands of planned PEP-II operations

Interaction Region Vacuum Chamber Upgrades p.26 of 25 HER- Downstream, “Forward”, “Right” HER- Upstream, “Backward”, “Left” IPQ2RQ4RQ5RFrangible LinkHigh-Power Dump IPQ2LQ4LQ5LFrangible Link “Luminosity Chamber” 10M Collimator 19.5M 9.4M8.4M 5.7M 3.6M 2.3M 3.6M 5.7M 7.7M8.5M10.1M11.4M 0.0 M